1. Field of the Invention
The present invention relates to a heat spreader, more specifically, to a heat spreader having a structure of improved heat transfer rate and thus enabling reliable heat spread characteristics regardless of its installation direction as well as of a light weight and small size.
2. Description of the Background Art
Recently, a Plasma Display Panel (hereinafter, referred to as “PDP”) TV which leads a large screen display market worldwide has a large screen and also an ultra slim type structure so that the PDP TV needs a small space for installation can be easily mounted on a wall. However, a 42 inch PDP TV consuming about 350 W˜450 W power gives out most power as heat because of low converting efficiency from electric energy to light energy. Out of totally emitted heat, about 250 W heat is emitted from double glass plate of the PDP and about 100 W heat is emitted from an image signal unit and a power unit arranged near its rear surface. More specifically, about 150 W heat out of 250 W heat from the double glass plate is transferred to a front surface of the PDP by natural convention and radiation, while about 100 W heat out of the 250 W heat from the double glass plate is transferred to a rear surface by conduction.
Accordingly, temperature on front surface of the PDP is getting higher and higher to be about 50° C. by the heat of 150 W transferred to the front surface of the PDP, thereby causing users to feel unpleasantness and inconvenience. For this reason, manufacturers have made an effort to decrease heat transferred to the front surface.
As a part of such an effort, a PDP chassis base mounted at a rear surface of a PDP is made of an aluminum plate with a thickness of about 1.5˜2.5 mm so that heat is conducted to the aluminum plate to be transferred to the rear surface. In spite of this effort, when heat distribution in the surface thereof is not uniform, and when a white image combined with 3 primary colors is locally displayed for a long time, excessive heat is concentrated locally therein, and thus an afterimage of the white image is displayed for minutes even after the white image has been removed, thereby causing a degradation in image quality.
In addition, a heat sink is used to emit heat generated in a CPU of an electronic device and in an electronic communication component such as a signal-amplifying module of a mobile communication repeater. In this case, when heat is generated locally in a highly integrated electronic component, the heat can not be spread effectively to a cooling fin of the heat sink through a heat spreader of the heat sink. In order to improve heat spread performance, in a conventional art, a method of decreasing heat spread resistance by thickening a thickness of a heat spreader of a heat sink made of aluminum or copper is used. But this method has disadvantageous effects that the heat sink cannot be installed in a small space due to an excessive increased weight and volume.
In order to solve such a problem, an invention (hereinafter, referred to as ‘known invention 1’) reducing an installation space by forming a depressed portion 14, 17 is disclosed in Korean Patent Publication Laid-Open No. 2002-0083712. However, the invention 1 has still defects that a thickness of heat sink should be thickened in order to decrease heat spread resistance.
In addition, as another method to spread heat generated locally, a heat spreader including a plate-shaped heat pipe to using a principle of a classical heat pipe is disclosed in Korean Patent Publication Laid-Open No. 2003-0042652. Such a type of heat spreader can be made a thin film structure, thereby having a small size and a lightweight and also having excellent heat spread performance. But the type of heat spreader is applied to very-limited area due to occurring a significant deterioration in performance since an internal space between two thin films has to be maintained in a vacuum, heat spread performance is deteriorated by a change of a degree of vacuum in the internal space after the heat spreader is used for a long time, and if the heat pipe is installed in such a manner that its longitudinal direction is vertical to a gravity direction, the performance of the heat pipe becomes deteriorated because it is difficult for a refrigerant to return against gravity in view of characteristics of the heat pipe.